Food Poisoning: Symptoms, Causes and Diagnosis

Food poisoning is also called as foodborne illness. The illness is caused by eating contaminated food. The most common causes of food poisoning are infectious organisms such as, bacteria, viruses and parasites or their toxins.

Updated: December 20, 2017

Food poisoning is also called as food-borne illness. The illness is caused by eating contaminated food. The most common causes of food poisoning are infectious organisms such as, bacteria, viruses and parasites or their toxins.
The bacteria could be salmonella or Escherichia coli (E. coli) and the virus, norovirus.
Infectious organisms or their toxins can contaminate food at any point of processing or production. Contamination can also occur at home if food is incorrectly handled or cooked.
It is not usually serious and most people get better within a few days without treatment.

Signs and symptoms:

Symptoms can vary depending on the source of the infection. The length of time it takes for symptoms to appear also depends on the source of the infection. It can range from as little as 1 hour to as long as 28 days. Sickness caused by food poisoning generally lasts from a few hours to several days.
Most types of food poisoning cause one or more of the following signs and symptoms:

  •     feeling sick or nausea
  •     vomiting
  •     diarrhea, which may contain blood or mucus
  •     stomach cramps and abdominal pain
  •     a lack of energy and weakness
  •     loss of appetite
  •     fever
  •     aching muscles
  •     chills

When to see a doctor?

If you experience any of the following signs or symptoms contact your doctor.

  • Frequent or repeated vomiting and incapable of keeping liquids down
  • Bloody vomit or stools
  • Diarrhea for more than three days
  • Extreme pain or severe abdominal cramping
  • Signs or symptoms of dehydration  such as confusion, a rapid heartbeat, excessive thirst, dry mouth, little or no urination, severe weakness, dizziness, or lightheadedness
  • Neurological symptoms such as blurry vision, muscle weakness and tingling in the arms

Also you should visit a doctor if:

  • you are pregnant
  • you are over 60
  • your baby or young child has suspected food poisoning
  • you have a long-term underlying condition, such as inflammatory bowel disease (IBD), heart valve disease, diabetes or kidney disease
  • you have a weak immune system because of medication, cancer treatment or HIV

How is food contaminated?

Food can become contaminated at any stage during production, processing or cooking. Most often the cause of contamination is the transfer of harmful organisms from one surface to another. This especially happens in case of raw, ready-to-eat foods, such as salads or other produce. Pathogens can be found on almost all of the food that humans eat. However, heat from cooking usually kills pathogens on food. Because the raw foods are not cooked, harmful organisms are not destroyed before eating and can cause food poisoning.
Meat, eggs, and dairy products are frequently contaminated. Water may also be contaminated with organisms that cause illness.
Food can be contaminated by:

  •     not cooking food thoroughly (particularly meat)
  •     not correctly storing food that needs to be chilled at below 5C
  •     leaving cooked food for too long at warm temperatures
  •     not sufficiently reheating previously cooked food
  •     someone who is ill or who has dirty hands touching the food
  •     eating food that has passed its use by date or expired
  •     the spread of bacteria between contaminated foods (cross-contamination)

Diagnosis of Food Poisoning:

Food poisoning can be diagnosed based on a detailed history, your symptoms and specific foods you have eaten. In severe cases, blood tests, stool tests, and tests on food that you have eaten may be conducted to determine what is responsible for the food poisoning. Sometimes a urine test can be done to evaluate whether an individual is dehydrated as a result of food poisoning.
A stool culture is done by sending a sample of your stool to a laboratory, where a technician will try to identify the infectious organism.  If an organism is found, your doctor likely will notify your local health department to determine if the food poisoning is linked to an outbreak.



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